Meet Karen Lewis, the Union Leader at the Center of the Chicago Teachers Strike

Fighting against the famously sharp-tongued mayor of Chicago is Karen Lewis, a relative newcomer to union leadership who now commands an army of 29,000 teachers and support staff in the nation's third largest school district

Rahm Emanuel, the famously sharp-tongued mayor of Chicago, may have met his match in Karen Lewis, a relative newcomer to union leadership who has taken a hard line against the city’s reform efforts. As head of the Chicago Teachers Union (CTU), Lewis commands an army of 29,000 teachers and support staff in the nation’s third largest school district. She taught high school chemistry for more than two decades and is known for being blunt. Last week, after 10 months of negotiations between the union and Chicago Public Schools failed to yield a new contract, Lewis called the mayor “a liar and a bully” and on Sunday threw a dig at charter schools, saying “real schools” would not be open when union members went on strike yesterday.

The issues up for negotiation in Chicago are similar to what is being debated in many school districts nationwide as new teachers’ contracts are hammered out in an environment that increasingly favors reforms like factoring student performance on standardized tests into teacher evaluations and disavows policies favored by educators like teacher tenure and a “last in, first out” approach to layoffs that prioritizes experience over all other teaching qualifications. CTU members say they are fighting for a “fair contract,” one that includes better benefits and working conditions as well as a teacher evaluation system they agree with and a way to recall recently laid-off teachers when there are new job openings. On Sunday night, union representatives reportedly rejected a contract that included a 16% pay increase over four years, opting to go on strike less than a week after the new school year began. As a result, instead of heading off to school on Monday, teachers formed picket lines as libraries, churches and other organizations struggled to help keep the district’s 350,000 or so students safe (and out of trouble).

While the issues are inherently contentious, especially when the school district is facing a budget deficit of $3 billion over the next three years, part of the fight may have something to do with the hot-headed personalities behind it. As one Chicago alderman put it the relationship between Emanuel and Lewis is like “gasoline and fire.”

But while much is known about the former White House chief of staff, his opponent is newer to the national stage. Lewis has served as the head of CTU since June 2010. Prior to becoming union president, she was a high school chemistry teacher for 22 years. She has teaching in her blood—both of her parents were teachers in Chicago and so was her husband, who is now retired. She grew up attending Chicago’s Kozminski Elementary School and Kenwood High School. For college, she started out at Mount Holyoke College and transferred to Dartmouth College, where according to her bio on the union’s website, she was the only black woman in the class of ’74. “People are impressed,” Lewis said in a speech last fall at a teachers union conference in Seattle. “Let me tell you, I spent those [college] years, smoking lots of weed, self-medicating.”

“I’m sorry, there are kids here,” she added as some audience members chuckled, “I wasn’t supposed to say that, right? Too late.”

Since assuming the role of CTU president, she has been outspoken about favoring teacher tenure and student equity while opposing merit-based pay and the privatization of public education. Emanuel isn’t the first public official she has lashed out at in public. At her Seattle speech last fall, Lewis mocked Education Secretary, and former Chicago Public Schools chief, Arne Duncan, imitating his lisp. (“Now, you know he went to private school ‘cause if he had gone to public school he would have had that lisp fixed,” she said on stage. “I know – that was ugly, wasn’t it? I’m sorry.”)

Despite, or perhaps because of, Lewis’ bold, if unpolished, approach, Chicago magazine wrote earlier this year that the union members were “solidly behind her” as she positioned herself as a “potential roadblock to Mayor Emanuel’s efforts to remake Chicago’s public schools.” The magazine also included Lewis on its 2012 “100 most powerful Chicagoans” list.

While Emanuel, who according to the Chicago Tribune has not been at the negotiations table because of “bad blood” between him and Lewis, called the strike a “strike of choice” on the same night that Lewis called the strike a “education-justice fight.” All eyes are on Chicago to see which of them gets the last word.

Kayla Webley is a Staff Writer at TIME. Find her on Twitter at @kaylawebley, on Facebook or on Google+. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.